I... don't think Dire Bats provide the necessary (type of) guano. The high sulphur content found in smaller bats is mostly resultant from a diet of insects. Same with the diets of the types of birds which offer a similar product.

On the other hand- a very easily raised bird can, generally, provide a high sulfide waste with similar properties. Chickens. Who, while being the nastiest avian on earth short of the buzzard, are largely available and fairly easy to farm throughout most of the inhabited world.